Textbook of Engineering Drawing, Second Edition

__ ~lsometric Projection 9.7

9.3.1 Box Method (Fig. 9.8)

When an object contains a number of non-isometric lines, the isometric drawing may be conveniently

constructed by using the box method. In this method, the object is imagined to be enclosed in a

rectrangular box and both isometric and non-isometric lines are located by their respective points

of contact with the surfaces and edges of the box.

15

~

• co
  10 15 ..,


• ----~·t
  50

(al

(b)

Fig.9.S

9.3.2 Off-set Method

Off-set method of making an isometric drawing is preferred when the object contains irregular

curved surfaces. In the off-set method, the curved feature may be obtained by plotting the points

on the curve, located by the measurements along isometric lines. Figure 9.9 illustrates the application

of this method.

9.4 Isometric Projection of Planes

Problem: Draw the isometric projection of a rectangle of 100mm and 70mm sides if its

plane is (a) Vertical and (b) Hirizontal.

Constructon (9.10)